Cynthia Thurlow likes to remind her patients that digestion begins in the brain, in the way people think about their food before they have even taken a bite. Conversely, 95 percent of the mood-regulating neurotransmitter serotonin, which is targeted by conventional anti-depressant drugs, is produced in the gut.
It is a reversal in the way we have been taught to think about food and mood.
The gut microbiome—the range of microoganisms in the gut, including bacteria, fungi and viruses-play a major role in the bidirectional communication between the gut and the brain.
Researchers in Finland recently found a link between a specific gut microbe, Morgariella, and depression. This is further evidence that people with mental health conditions often have very different microbes in their gut.
Alterations in the composition of gut microbiota are implicated in causing leaky gut(an increased permeability of the gut barrier), activating systemic inflammation, affecting the efficacy of serotonin and changing levels of brain-derived neurotrophic factor (BDNF).
However, a Chinese study last year found that intermittent fasting enriched the gut composition of diabetic mice and pointed to several other potential benefits, including increased microbial diversity, reduced inflammation and increased production of short-chain fatty acids, which inhibit the growth of bad bacteria.
When it is time to break the fast, the Mediterranean diet, abundant in plant-based ingredients, fiber and omega-3 fatty acids, has been found to establish a diverse microbiome associated with protection against depression. Aromatic spices and herbs such as oregano, rosemary and thyme common to that diet are also good for gut microbiota.
A Harvard study of over 80,000 nurses found that a diet high in flavonoids is associated with lower risk for depression, especially among older women.
Two clinical trials also found that high-flavonoid fruit and vegetable intake led to significant improvements in cognitive performance and increases in serum BDNF levels